Vein Formation and Reopening in a Cooling Yet Intermittently Pressurized Hydrothermal System: The Single-Intrusion Tongchang Porphyry Cu Deposit

Porphyry deposits are the dominant sources of copper and major several base precious metals. They commonly formed via repeated emplacement hydrous magmas associated fluid exsolution. As a result, mineralized hydrothermal veins may undergo multiple deposition reopening processes that not fully accounted for by existing models. The Tongchang porphyry Cu deposit is rare example being related to single intrusion. simplicity in intrusive history provides an ideal starting point studying more complex multi-intrusion systems. Detailed scanning electron microscope (SEM) cathodoluminescence imaging (CL) revealed rich microtextures quartz anhydrite timeline encompassing early followed fluid-aided dynamic recrystallization, which was succeeded intermediate stage dissolution subsequent deposition, ended with late continuous brecciation, fracturing. Vein common than expected. Fifteen out seventeen examined vein samples contained and/or older or younger age defined sequences. Thermobarometry solubility analysis suggests events occurred general cooling path (from 650 °C 250 °C), interspersed two episodes pressurization. first episode at high-T (>500 under lithostatic conditions alongside whereas second one took place lower temperature (~400 hydrostatic transition conditions. main chalcopyrite veining overpressure temperatures 380–300 °C. results this study reaffirm thermal hydraulic causative factors growth deposits.